The US president, Donald Trump, and a number of Saudi Arabian regional leaders visit the new Global Centre for Combating Extremist Ideology in Riyadh on Sunday. The heart of the centre is a giant wall filled with screens displaying real-time online extremist activity. Trump, the Saudi king, Salman bin Abdulaziz al-Saud, the Egyptian president, Abdel Fattah al-Sisi, and Melania Trump placed their hands on a miniature globe, officially activating the centre and launching a futuristic welcome video